It has been well known that the gases which are contained in exhaust gases of automobiles, for example nitrogen oxide (NO.sub.x) gas and carbon monoxide (CO) gas, are very toxic, hence the gases should be ejected for health care.
Especially, in such places underground parking lots, while the gases are accumulated in some places, a ventilation system is required for ejecting the toxic gases and lowering the amount of the gas under the predetermined limit.
A ventilation system having ducts is an example of the existing ventilation system for ventilating such a large space.
However, in such a system, air flow is formed only between supply ports and exhaust ports of the system, hence the toxic gases may be accumulated in the place where is far away from the position the ports are installed.
In order to make up for the above shortcomings, it is required that the supply ports and the exhaust ports are installed more, then, the cost for the system runs higher as more ports are installed.
In addition, there is another shortcoming in such a system in that there are constraints in installing the ducts because in most cases there are many obstructive structures, such as large posts, ducts for cable, pipes for water suppling, and so on in the place where the system is installed.
In the meanwhile, in order to make up for the disadvantages of the ventilation system, a ventilation system without ducts has been disclosed in Japanese laid-open patent publication (No. 97-273785(HeiSei 9-273785) dated Oct. 21, 1997).
In the ventilation system, as shown in FIGS. 1, 2a, 2b, and 2c, a blower 3 is installed in a box shape ventilating unit 1, and inlets 4 and nozzles 5 are fixed rotatably in holes 7 at the side plane 6 of a chamber 2 by means of flanges 8 and lugs 9.
When the ventilating unit 1 is installed in underground parking lots, as shown in FIG. 1, the ventilating unit 1 is placed to face the inlet 4 of another ventilating unit 1 one after another in order to carry the air flow through the entire space.
But in such a system, while the direction of air jet can be controlled within very small degrees and outlets of the nozzles 5 are inclined from the center line of the nozzle, so the flow of air cannot be controlled in various directions, therefore, the system should be installed along straight line or close to the straight line.
Moreover, as shown in FIG. 2c, because the base of the nozzles 5 are installed vertically to the wall plane of the chamber 2, there is air resistance in nozzles 5 with the wall plane, therefore, the distance which air can reach is getting shorter and the noise from the air resistance occurs.